1. Field of the Invention
The present invention relates to a power steering system for a vehicle.
2. Description of the Background Art
A known power steering system is shown in FIG. 3, and comprises a power assist cylinder 3 provided between a steering shaft 1 and a vehicle body frame 2, a control valve 4 operated by the steering shaft 1 to control the power assist cylinder 3, an oil pump 5 for pressurizing a working oil supplied to the power assist cylinder 3, and an oil tank 6 for reserving the working oil. The oil tank 6 is an open-to-atmosphere type, and is fitted to the vehicle body frame 2.
The oil pump 5, the oil tank 6 and the control valve 4 are communicated with each other by three oil pipes 7. An input shaft 8 is fixed to a lower end portion of the steering shaft 1 by welding, and a spool lever 9 for operating the control valve 4 is fastened and fixed to the steering shaft 1 through a clamp member 9b. An output shaft 9a to which the power assist cylinder 3 is connected is connected to the input shaft 8.
In the background art as above-mentioned, the input shaft 8 is fixed to a lower end portion of the steering shaft 1 by welding. The output shaft 9a to which the power assist cylinder 3 is connected is connected to the input shaft 8, so that a power assist portion including the power assist cylinder 3 and the control valve 4 and a steering shaft portion including the output shaft must be separately assembled onto a vehicle body, and there is the problem that much time is required for assembly.
In addition, since the spool lever 9 for operating the control valve 4 is fastened and fixed to the steering shaft 1 through a clamp member 9b, the condition of fastening has an influence on assembly accuracy.
The present invention has been made in consideration of the above-mentioned problems in the background art, and it is an object of the present invention to provide a power steering system with which it is possible to simplify the assembly onto a vehicle body and to enhance assembly accuracy.
In order to attain the above object, the power steering system of the present invention comprises a steering shaft turnably fitted to a vehicle body frame, a power assist cylinder provided between the steering shaft and the vehicle body frame, a control valve operated by the steering shaft to control the power assist cylinder, and a spool lever fitted to the steering shaft for operating the control valve. The power steering system is characterized in that the steering shaft is divided into two portions in the axial direction to set the lower portion to be an input shaft, and a connecting cylinder to which the input shaft is spline-fitted is integrally provided at a lower portion of the steering shaft. A side wall of the connecting cylinder is provided with a groove in the axial direction, and a fastening means is provided for reducing the diameter of the connecting cylinder so as to reduce the width of the groove. The spool lever is integrally fitted to the input shaft.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.